Pneumatic tool



W. 'A. SMITH ET AL PNEUMATIC TOOL Filed'May 2, 1921 3 Sheets-Sheet l March 2,1926. f v1,574,762

W. A. SMITH ET AL PNEUMATIG TOOL Filed May 2, 1921- 5 Sheets-Sheet 2 if/29.4. I

M5 1 A LQHA/EYS March. 2 1926.

w. A. SMITH ETAI.

`PNEUMATIC TOOL Filed May 2. 1923, A 5 Sheets-Sheet 5 lll 'alternatively admitting fluid f on opposite sides thereof.`

Patented li/ilar. '2, i926.

naar r"rua WILLAM A. SMITH AND CLARENCE H.

sreivoas To cnioaefo reafirmar or new JERSEY.

AApplication filed May 2,

TOQZ whom. it may concern:

'Be it known that we, WILLIAM A. SMITH and @Lamentin Il.. DociiHAM. both citizens of the United States of America, residing 'at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Pneumatic Tools, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to percussive tools of that type in which a free flying piston is controlled in its movements by a`valve under pressure The invention hasjnore particular referenceftowthe construction of thevcontr'llig valve` and the means for operating the same as more fully i hereinafterset forth.

' one end of its stroke7 In the drawings: i v Figure l is a. longitudinal section through the tool and valve, showing the pistonat and a valve set. for returning the same; i

Figure Q is a similar View with the piston stroke and the valve set for again driving the piston forward g A Figure 3 is a View similar to Figures l and 9. Ashowing a modified construction of valve.; I i Figure 4t is asimilar view showing still another modification of the valve;

Figures and 6 are views similar to Figures l and 2 showmganothermodification;

Figure Fig. 5; y

Figure S is an end elevation of the valve.

A is the main cylinder for `containini;r the free flying` piston B and which is provided with a central annular exhaust passage C communicating with the exhaust port l) The piston B is'provided with a shank F. fitting an extension F of the cylinderof 7 is a section `on line 7-7 of `reduced diameter and the end of this shank is adapted to impinge against the tool 'G mounted in said extension.

T he valve H occupies a cylinder I at one side of the main cylinder A and comprises essentially end head 'portions Hl and H2, a central head or disk Hfs and intermediate grooves or annular chambers H4 and H5 forming the main air feeding passages.

-rockin-ila, or DETROIT, MLCHIGAN, As- :eNEU'ii/LATIC T001. contraint, oF NEW YORK, v1v.. Y., A con- PNEUMATIC TOOL.

1921. serial No. 466,189.

Surrounding the valve within the cylinder I are bushings J and J and centrally between 4 said bushings 1s formed an annular port la controlled by the disk Hato be placed alternately in communication with 'the grooves H and H5.

The shifting of the valve is controlled by the conjoint action of leak ports establishing communication from the main air supply to the opposite ends of the valve cylinder I, and exhaust ports leading from said opposite endspf the valve cylinder to the main cylinder at points intermediate the annular exhaustJ passage and the end of the cylinder. These exhaust ports are therefore sealed by the piston before it has reached the end ofits stroke, which permits the building up of pressure in the end of the valve cylinder to shift .the valve. As shown, L and L are the leak passages which'are formed respectively in the bushings .l and J and extend from the main air channel to `the ends of the valve cylinder. These passages are sufficiently restricted so that when the valve cylinder is .in communication with 'the exhaust, the pressure in said cylinder is not materially raised by the leakage.' On

the other hand, whenever the exhaust conrise.- M and M are the lexhaust passages leading from the opposite ends of the valve cylinder to the main cylinder and, as shown,

the ports N and N"openi ng into the main cylinder are located upon opposite lsides of the annular exhaust channel C and af considerable distance from the end of the cyl-. inder. The valve cylinder I .is further provided with exhaust ports O and O which l are controlled by the heads H and H2 of the valve. These ports communicate with annular channels P and P `in the bushings tl and J', the arrangei'i'ient being such that when the valve is at the end of thc cylinder adjacent to one of said channels, the latter will be in open connnnnication with the annular airchannel in said valve, Aso that any pressure within said channel and the main cylinder in communication. therea V with may be exhausted. These channels also intercept any leakage past the heads H and H2 from one side to the other thereof. R and R are passages extending from the opposite ends of the maincylinder to the heads H, H2 and the disk H3.-

lVith the construction as thus far de-.

scribed, in operation, the pressure fluid, such as compressed agir, entering 'through the channel Q will be in communication through the annular port K- with oneor theother of the valve channels H4 and H5, according to the position of the valve. As shownin Fig- Iure 1, the piston B is in a position at the end of its forward stroke and the valve H is shifted to the rightfhand end of the valve cylinder, so that communication is established from the channel Q. through the port K, channel H.4 and passage R to the lefthand end of the cylinder A. This pressure is therefore operating to return the piston, while the opposite end of the nel C.

The movement of the piston in its return stroke closes the exhaust channel C and then the port N l of the exhaust passage M from the valve cylinder, which permits the building up of pressure at the right-hand end of said valve cylinder. After the piston has over-ridden the` port N and the exhaust channel C, the pressure in the chamber on the left-hand end of said piston Will be exhausted and also the' pressure on the lefthand end of the valve. This permits the built up pressure at the right-hand end of the valveeylinder to quickly shift the valve, cutting olf communication between the anl` nular port K and channel H4 and establishing communication between said port'and passage` H5, the parts being in the posltion shown in Figure 2. The high pressure fluid is thereforeadinitted to the'main cylinder at the right-hand end thereof, While at the same time the annular port P is placed in communication With the channel H4 so that in the forward stroke of the piston the fluid on the left-hand side thereof can be` exhausted through the port O.

In the construction shown in` Figure 3 the valve heads H', H2 and disk Hs are of equal` diameters which equalizes the pressure areas on said disk and on the inner faces of the heads H and H2. I prefer, however, a construction in which the area of the disk is somewhat in excess of that Aof the end heads and as shown in Figures 1 and 2, the disk is of slightly g'reaterdiaineter and slides in a `port-ion S of enlarged diameter in the bushings J and J. Thus the pressure of' the fluid Within the channels H* and H5 which is exerted opposi'tely upon the vend heads and the central disk, has a differential tending tohold the valve in position Without regard to the pressure Which is exerted on the end of the valve.

In the modified construction shown in lFigure 4 the central disk H3, instead of forming peripheral contactwith the cylincylinder is in, free communication with the exhaust lchaninder,

-Valve cylinder` which will cause the valve to operate as before described.

The double exhaust for the piston chamber is provided in order that any leakage of air past the valve disk H3 after the main exhaust channel G has been covered by the piston at the beginning of its stroke, due to a worn valve, will be taken care of by the auxiliary exhaust ports O -and O. The auxiliary exhaust ports also perform` the function of providing a vent to atmosphere for the small amount of air passing from the restricted leak passages L and L into the cylinder through the ports M N or M N. It will be thnsapparent that by providing the auxiliary exhaust ports O and O excessive compression in the ends of the cylinder is avoided and that the period of such compression on each stroke is delayed to the latest possible moment thereby making possible a very free acting piston with a minimum of back pressure.

that we claim as our ini'entionis:

l. In a fluid pressure operated tool, a cylinder, apiston reciprocable therein, said cylinder having a main exhaust port overrun by said piston,- motive fluid inlet passages opening into said cylinder adjacent the ends thereof, a valve controlling the movements of .said piston and arranged to admit motive fluid in alternationfto said passages, means for shifting said valve in timed relation with the inoiements of said piston including a passage supplying motive fluid continuously in limited amount to one pressure area of said valve, a valve controlling exhaust passage extending from said area to said cylinder intermediate said main exhaust port and one end of said cylinder, and auxiliary exhaust means controlled by saidvalve 'for said end of the cylinder whereby the full cured and any tendency of the valve to shift prior to the closing of said valve controlling exhaust passage by said piston is avoided.

2. In a fluid pressure operated tool, a cyla-piston reciprocable therein, said cylinder having a main exhaust port overrun by said piston, motive fiuid inlet passages opening into said'eylinder adjacent the ends thereof, a valve lcontrollingtlie movements of said piston and arranged to ends thereof, a valve controlling the move tween the latter and said motive fluid inletl passages, and an auxiliary exhaustifor one end ot said cylinder under control of said valve tor insuring a full stroke of the piston toward said end and for avoiding any tending of the valve controlling exhaust passage at said end of' the cylinder by the piston.

ln a fluid pressure operated tool, a c vlinder, a piston reciprocable therein, said cylinder having amain exhaust port overrun by said piston, motive fluid inlet passagesopening into said cylinder adjacent the ments of said piston and arranged to admit motive liuid in alternation to said passages,

said valve having opposed pressure areas, passages admitting motive fluid lcontinuouslimited amount to said areas, valve controlling exhaust passages from said areas opening into said cylinder on-opposite sides of said main exhaust port and between the latter and said motive tluid inlet passages, and auxiliary exhaust means for bothends ofv said cylinder under control of said valve in alternation with the admission` of motive.

duid to said ends for insuring full strokes ot said piston in both directions-and for avoiding any tendency of the valve to shift until the respective valve controlling exhaust ports are closed by the piston.

si. ln a lluid pressure operated tool, a cylinder, 'a piston reciprocalole therein, said cylinder having 'a main exhaust port overrun by said piston and passages opening into said cylinder' adyacentlihe ends thereof, a valve controlling the movement of said piston and arrangedalternately to effect comn munieation oi' said passages with the motive 'lluid inlet and with an auxiliary exhaust, said valve having opposed pressure areas, passages admitting motive fluid continuously in limited amount to said areas, and valve controlling exhaust passages from said areas opening into said cylinder on opposite sides ot' said `main exhaust port and intermediate the latter and said 'Iirst named passages thereby to insure delay in the shifting et said valve near the end of each stroke of the. piston until after the'respective valve controlling exhaust passagevis closed by the' piston. l

5. rl^he combination oli a piston, a valve having end heads, a centralr` disk and chamincluding cylinder having bers letvveen said heads and disk, a casing port over-run by said piston, a cylindrical casing rer said valve having a main 'fluid ency of the valve to shift lprior to the clos-` a main exhaust supply port alternately communicating with the chambers ot said valve in dilierent posiltions of adjustment thereof, leak passages extending from the main air 'passage to chambers at opposite ends of sai'd valve, exhaust passages extending respectively `from the opposite ends ci said valve'casing to said cylinder Vat points on opposite sides of said main exhaust passage and'intermediate the same and the ends of the cylinder, passages in communication With the chanibers of said valve extending to opposite ends of thecylinder,and auxiliary exhaust ports alternatively in communication with said chambers of the valve. .i 4

6.,.The combination of a` piston, a valve having. end heads and a central disk of larger diameter with chambers intermediate said disk andsaid heads, a easing including a'cylinder having'a main exhaust port over- 85 run by-'said piston, a valve casing having a A main air port controlled by said central disk to' be placed in alternative communication with said valve chambers, passages respectively communicating with said chambers and leading to the opposite ends of said cylinder, Huid leak 'passages extending to chambers at opposite ends of said valve, passages extending from said end chambers to. ,said cylinder on opposite sides of said main exhaust passage and intermediate the same and the en ds of" the cylinder, and'annular grooves surrounding said end heads and provided with exhaust ports, said grooves lceing alternatively placed in communication A with the chambersof said valve and intercepting leakage from the ends of the valve to said chambers. Y 1

7. The combination. ot a piston, a cylinder having an exhaust port over-run by said piston, a vtlv'e for controlling the movements of said piston, a leak passageor cont uously admitting motive fluid in limi i amount to a pressure area ot said valve, ad a Valve-controlling exhaust passage for saidA pressure area communicating with said cylinder at a point intermediate the main`exhaust therefor and one end et the cylinder thereby to elifect shitting of the valveby built up pressure '-.vhen'said -valve-controlila ling exhaust-passage is closed by said piston and to relieve said pressure through said cylinder exhaust when the piston uncovers f said valve controlling exhaust passage and overruns said exhaust portn y 8. The combination ot. a piston, a valve controlling the movements oit said piston, a easing orming a. cylinder for said piston and also housing said valve, said cylinder being provided with a main exhaust port over-run 125 by said piston, auxiliary exhaust means controlled by said valve for one end ot' said cylinder, and valve-controlling exhaust ports communicating with said cylinder on oppo-l site sides of said main exhaust port and relas corresponding .on opposite sides spectively sealed by said` piston at opposite ends of its stroke, and niotive'luid leak passages for building up opposing pressures on said valve respectively on the sealing of the valve-controlling exhaust ports.

9. The combination of a piston` a valve controlling the movement of said piston, a easing forming a cxrf'linder for said piston and also-a housing for said valve, said cylinder having a niain exhaust port over-run by said piston, auxiliary exhaust means controlled by said valve tor both ends of said cylinder, and a pair ot' val\"e-Controlling exhaust ports communicating with the cylinder and between the saine and the opposite ends of the cylinder, said valve-controlling exliaustports being respectively sealed-by the piston when at the opposite ends of its stroke, and inet-ive fluid leak passages for building up opposing pressures on said valve when the respective controllingr exhaust ports are sealed.

10. The combination of a piston; a valve having end heads of'equal diameter and a of said niain exhaust port exhaust port overa-un by said piston, a valve 30 cylinder having a main air port controlled by said Central disk to be placed in alternative communication with said Valve chambers, passages respectively communicating With said valve chambers and leading to the opposite ends of said cylinder, fluid leak passages extending to chambers at the 0 Uposite ends of said valve, and passages'extending from said end chambers to said cylinder on opposite sides of said inain exhaust passage and intermediate the' saine and the ends of the cylinder, said passages being alternately sealed by said piston to cause the building up of pressure in the connecting chamber at the end of the valve for shifting the same, and the differential area of said central disk in excess of said end head tending to hold said Valve in shifted position.

In testimony whereof we afix our signatures.

VILLIAM A. SMITH. CLARENCE H. DOCKHAM. 

